1. Field of the Invention
The present invention relates to a method for controlling operating state of an internal combustion engine.
2. Description of Background Information
There are well known control methods in which various parameters of the engine operation are detected and the operating state of the multi cylinder internal combustion engine is controlled through a calculation of an optimum amount of the fuel supply for the engine operation of the moment, according to detected output signals of the parameters.
As an example of the control method of this type, the present applicant has already proposed, in Japanese patent Application No. 57-055890, a method in which major parameters of the engine operation are continuously detected by sensors, and sampled in accordance with a TDC (Top Dead Center) signal which is synchronized with the rotation of the engine crankshaft. The fuel supply amount is determined in accordance with a corrected value of the sampled value which is obtained by adding a latest sampled value to a value responsive to the difference between the latest sampled value and a preceding sampled value.
In such a control method as described above, a vacuum level in an intake air passage of the engine is detected as a major parameter of the engine operation, for instance, by means of an absolute pressure sensor.
However, in the conventional control method in which the sampled values of the sensor output signals are corrected in such a manner as described above, a drawback was that an overshoot (excessive increase) of the corrected value of the latest sampled value tends to appear, especially when the operating condition of the engine is changed very rapidly, for example, at a full throttle operation of the engine. If such an overshoot of the corrected value occurs, the fuel supply amount will be excessively increased, which in turn will result in an adverse effect to the air/fuel ratio control, such as the supply of an overrich mixture to the engine.
For other devices to be operated by a calculated control signal such as the exhaust gas recirculation amount, there are no problems if the corrected value of the sensor output signal is not used, due to rather slow response characteristics of those devices.